New tiny implant could be game-changer for neurological disorders

A tiny new implant capable of firing light into the brain to control neurons is substantially better than existing methods.

For a growing number of people living with a neurological disorder, optogenetic devices are being used to help stop or alleviate many of the worst symptoms. The technique uses light to turn specific neuron groups in the brain on and off.

For example, researchers might use optogenetic stimulation to restore movement in case of paralysis or, in the future, to turn off the areas of the brain or spine that cause pain, eliminating the need for – and the increasing dependence on – opioids and other painkillers.

However, current optogenetic technology is bulky and often visibly attached to the outside of the skull. Additionally, some devices don’t allow for precise control of the light’s frequency or intensity, and they can only stimulate one area of the brain at a time.

Now, researchers working at the University of Arizona have revealed a tiny, battery-free implant that could make treatment substantially easier for patients. Publishing its findings in Nature Electronics, the team behind the new device said it is able to digitally control the intensity and frequency of the light being emitted, and can also independently stimulate multiple places in the brain of the same subject.

The implant can be inserted using a simple procedure with no adverse effects and doesn’t degrade over time, unlike existing larger implants that need to be replaced every five to 15 years.

Combined image analysis with MRI and CT results superimposed on a 3D rendering of an animal implanted with device. Image: Philipp Gutruf

An efficient brain pacemaker

This ability to control the light’s intensity is critical because it allows researchers to control exactly how much of the brain the light is affecting, with brighter light able to reach further into the brain. It also means the operator can control the heat generated by the light sources, avoiding the accidental activation of other neurons.

The implants are powered by external oscillating magnetic fields, and a new antenna design has also solved a significant problem in previous optogenetic devices. This problem meant that the strength of the signal being transmitted to the device varied depending on the angle of the brain, with a person turning their head being enough to weaken the signal.

“This system has two antennas in one enclosure … we switch the signal back and forth very rapidly so we can power the implant at any orientation,” said Philipp Gutruf of the research team.

“In the future, this technique could provide battery-free implants that provide uninterrupted stimulation without the need to remove or replace the device, resulting in less-invasive procedures than current pacemaker or stimulation techniques.”

Another big advantage of the system is that it can be safely imaged using tomography and MRI, allowing for greater analysis of how the system is performing, as well as the state of bone and tissue, and the placement of the device.